Conventional article cleaning and drying apparatus employing electrically actuated functional means, such as clothes washers, dishwashers and clothes dryers, now enable automatic operation by a user with preselection of the desired processing modes and processing conditions. For example, a user can now automatically operate a conventional clothes washer and similar fabric article cleaning apparatus with an initial selection of the desired mode of operation such as a wash, rinse and spin cycle, as well as further preselect the processing conditions such as wash temperature, liquid levels and time duration for these selected operating modes. In a similar manner, selection of the operating modes in a conventional automatic dishwasher to include wash, rinse and the operating temperatures and time intervals for carrying out the preselected operating cycles. Moreover, conventional automatic clothes dryers now provide both time controlled and non-time controlled operation with a user also being enabled to preselect a termination of the drying cycle when a predetermined moisture content has been reached in the fabric articles being dried. It is further customary in such conventional article cleaning apparatus to perform preselected multiple modes of operation with a variety of electrically actuated functional means and which generally includes a rotatable device such as a wash tub, wash arm or drum member being employed depending upon the type of article cleaning apparatus involved. Automatic function control of the user selected processing modes is also now achieved in a conventional article cleaning apparatus with a variety of well known electrical control techniques to include temperature control circuits, timer circuits, pressure control means and still other type sensor operated circuitry. The function control is typically exercised in such conventional article cleaning apparatus by regulating electrical power to the selected functional means with some form of operatively associated relay means.
Piezoelectric relay devices are recognized to provide a means for either initiating or interrupting current flow to a load device. A known piezoceramic type relay device for this purpose is disclosed in U.S. Pat. Nos. 4,670,682 and 4,689,517, both assigned to the assignee of the present invention. The relay device includes a piezoceramic bender member formed by at least two planar piezoceramic plate elements secured in opposed parallel relationship sandwich fashion on opposite sides of at least one central conductive surface and having outer conductive surfaces that are insulated from each other and the central conductive surface by the respective intervening piezoceramic plate element thicknesses. Movable contacts associated with the movable bender coact with fixed contacts disposed thereby to either complete or interrupt an electrical circuit providing a current flow from a power source to the load device. A representative form of this type relay device as disclosed in the above mentioned prior art patents employs a piezoceramic bender member which is selectively prepoled with clamping means secured at non-poled portions adjacent to and mechanically supporting the selectively polarized bender member in a cantilever manner for operating pairs of coacting electrical contact means and with the non-poled portions being mechanically unstrained and electrically neutral. The bender member is made to operate either side of a center position normally assumed by the bender member in an unenergized condition to thereby enable different modes of operation. In one mode of operation, the relay device can simply serve as an on-off switch wherein one pair of coacting switch contacts either makes or breaks the electrical circuit with respect to the load device. In a different mode of operation, however, the pair of coacting switch contacts is provided on each side of the bender member to enable selective energization of multiple load devices. Both modes of operation with the prior art "bimorph" type bender switching devices are further said to be conducted in a similar manner wherein the DC energizing potential used to actuate deflection of the bender member has the same polarity as the polarity of the potential used to polarize the piezoceramic plate elements. The depolarization avoided by operating the relay devices in this manner provides dipole enhancement enabling relatively long term operation with load devices employing load voltages as high as 5000 volts and corresponding currents as high as hundreds of amperes.
In both above defined modes of operation, such piezoceramic relay devices have been recognized to afford major operational and structural advantages over either electromagnetic (EM) relays or semiconductor devices when employed in power switching applications. These advantages are reported in U.S. Pat. No. 4,658,154, also assigned to the assignee of the present invention, which further includes disclosure of piezoceramic relay switching circuits providing control of single and double load apparatus. The EM relays still widely employed for this purpose provide an interface between, for example, an electronic control circuit and a load circuit wherein the former handles the low power control signals for selectively energizing the relay coil to appropriately position the relay contacts coacting in the power circuit to switch relatively higher levels of power. When such relay contacts are closed, load current is conveyed, with virtually no losses and when they are parted load current is interrupted with the certainty only an air gap can provide. Over the years improvement in EM relays have resulted in increased efficiency and reduced physical size. That is, such relays can be actuated with control signals of rather low energy content to switch reasonably high levels of load current. For example, EM relays are available which can be actuated with a one watt control signal to switch several kilowatts of power at 115 or 230 volts AC. As a consequence, EM relays can be operated with signals generated by solid state control circuitry. On the other hand, the drawbacks associated with EM relays employed for controlling current flow in load circuits responsive to control signals still remains substantial. While current EM relays have been miniaturized as compared to earlier designs of such relays, their actuating power requirements are still quite large in contrast, for example, to state of the art solid state power switches. The current EM relays are still relatively complex and expensive to manufacture, for example, their coils typically require a multitude of turns of very fine wire. The coil resistance consumes some power which must be provided by a reasonably stiff power supply. When, for example, EM relays are utilized in home appliance controls, relay operating power must be derived from a 115 or 230 volt AC utility source. The requisite power supply, particularly when an EM relay is operatively associated with a solid state control circuit, requires a transformer, electrolytic capacitors, regulators and protection to insure a reliable source of relay actuating current. Such power supplies are both costly and constitute a significant source of power dissipation. Moreover, in certain applications where high ambient magnetic fields are present, such as in motor starter applications, EM relays must be specially shielded to discourage spurious operation. The drawbacks associated with employment of EM relays in power switching circuitry has thereby resulted in a trend toward utilizing solid state switches, such as SCRs, Triacs, Thyristors, MOSFETs, IGTs and the like as the power switching output device. While such solid state switches are becoming relatively inexpensive and may be smaller in physical size than comparably rated EM relays, they do present a rather significant "on" resistance, which, at high current levels, results in considerable power dissipation. Thus, semiconductor power switches being utilized at high current application must be properly heat-sinked for protection against thermally induced damage, and, as a consequence, with their heat-sinks can take up more physical space than do their EM relay counterparts. Moreover, solid state power switches must be protected against possible damage in spurious operation as a result of transients, electrostatic discharges (ESD) and electromagnetic interference (EMI). All these protective measures represent an additional expense. In that such solid state power switches do not impose an air gap to restrain the flow of current in their "off" condition and because of their "on" condition failure mode, Underwriters Laboratory has disapproved of their application in numerous domestic appliances. Such disapproval has only been overcome in part with a combination of the solid state switches and the EM relays in some domestic appliances so as to provide the required air gap.
All of the foregoing major disadvantages found with employment of either EM relays or semiconductor switches as the power switching output device has prompted renewed interest in piezoelectric relays, including piezoceramic devices. Recent improvements in piezoceramic materials have enhanced their electromechanical efficiency for these relay applications. Piezoceramic drive elements may be fabricated from a number of different polycrystalline ceramic materials such as barium titanate, lead zirconate titanate, lead metaniobate and the like which are precast and fired into a desired shape such as rectangular-shaped ceramic plates. The piezoceramic relay devices require very low actuating current, dissipate minimal power to maintain an actuated state and draw no current while in their quiescent or unenergized state. The electrical characteristics of the piezoceramic drive elements are basically capacitive in nature, and thus are essentially immune to ambient electromagnetic fields. Such piezoceramic relay devices can be designed in smaller physical size than comparably rated EM relays. Since piezoceramic relay devices utilize switch contacts, contact separation introdues the air gap in the load circuit as required for UL approval in domestic appliance applications. Closure of these relay contacts provides a current path of negligible resistance, and thus unlike solid state power switches, introduces essentially no loss in the load circuit. Since additional structural and operational advantages for such improved piezoceramic relay devices can be found in the aforementioned prior art U.S. Pat. Nos. 4,670,682 and 4,689,517, both disclosures are herein specifically incorporated into the present application in their entirety.
The suitability of piezoceramic relay devices in controlling current flow within a particular apparatus understandably requires still other factors to be considered. Both operational characteristics desired in the apparatus as well as environmental conditions being countered have to be satisfied. In a co-pending application Ser. No. 173,502, filed Mar. 25, 1988, and assigned to the present assignee, there is disclosed a control system for regulating electrical power input to the refrigeration mechanism or defrost mechanism in an atmospheric cooling apparatus, including domestic refrigeration appliances, which employs at least one piezoceramic relay device. In one embodiment, the control means employs individual piezoceramic relay devices for power regulation to the respective mechanisms while in a different embodiment a single piezoceramic relay device regulates power input between the refrigeration mechanism and defrost mechanism. In still another co-pending application Ser. No. 173,491, also filed Mar. 25, 1988, and assigned to the present assignee, there is disclosed a different control system for regulating electrical power input to the resistive heating elements of an electrical heating apparatus, including domestic cooking appliances, which employs at least one piezoceramic relay device. In one embodiment, the control means employs individual piezoceramic relay devices for power regulation to the individual heating elements while in a different embodiment a single piezoceramic relay device regulates power input to a pair of the heating elements. The circuitry actuating the piezoceramic relay devices in both of these control systems can be directly and ohmically connected to the power source in order to draw minimal actuating power directly from conventional 115 or 230 volt AC residential power sources. Since further operational and structural advantages for the disclosed control systems can be found in the aforementioned commonly assigned co-pending applications, both disclosures are also hereby specifically incorporated into the present application in their entirety. It will be apparent from the foregoing considerations as well as use already being made of piezoceramic relay devices in various type domestic appliances employing electrically actuated functional means that electrical power regulation in still different type apparatus can be more effectively provided with piezoceramic relay means.
It is a principal object of the present invention, therefore, to provide a more energy efficient system for the regulation of electrical power in an article cleaning apparatus employing multiple processing modes which are provided with electrically actuated functional means.
It is still another important object of the present invention to provide control means employing a plurality of piezoceramic relay means to regulate electrical power input in an article cleaning apparatus employing multiple processing cycles conducted with electrically actuated functional means.
Still another important object of the present invention is to provide improved electronic control means for automatic regulation of electrical power in an article cleaning apparatus employing multiple processing cycles provided with electrically actuated functional means.
A still further important object of the present invention is to provide a novel method for regulation of electrical power in an article cleaning apparatus employing multiple processing cycles achieved with electrically actuated functional means.
Still another important object of the present invention is to provide a method of operating piezoceramic relay means to more efficiently regulate electrical power input to an article cleaning apparatus having multiple processing cycles conducted with electrically actuated functional means.
Still another important object of the present invention is to provide a more efficient method to automatically regulate power input in an article cleaning apparatus employing multiple processing cycles which are provided with electrically actuated functional means.
Another important object of the present invention is to provide a more efficient article cleaning apparatus utilizing novel control means to more effectively regulate electrical power input to a plurality of electrically actuated functional means providing multiple processing cycles in the apparatus.
Another important object of the present invention is to provide control means regulating electrical power input in an article cleaning apparatus utilizing multiple processing cycles provided with electrically actuated functional means in a manner avoiding unintended simultaneous operation of the respective functional means.
Still another important object of the present invention is to provide an electrically operated article cleaning apparatus employing multiple processing cycles with simpler and lower cost control means to regulate electrical power input in the apparatus.
A still further important object of the present invention is to provide an electrically operated article cleaning apparatus employing multiple processing cycles with improved electronic control means to automatically regulate electrical power input to the individual processing means.
Another object of the present invention is to provide an electrically operated fabric laundering apparatus utilizing novel control means regulating the electrical power input.
Another important object of the present invention is to provide an electrically operated dishwashing apparatus utilizing novel control means regulating the electrical power input.
Still another important object of the present invention is to provide an electrically operated fabric drying apparatus utilizing novel control means regulating the electrical power input.
These and still other objects of the present invention will become apparent upon considering the following detailed description for the present invention.